Presence and frequency of rare circulating tumor cells (CTCs) in bloodstreams of cancer patients are pivotal to early cancer detection and treatment monitoring. Here, we use a spiral microchannel with inherent centrifugal forces for continuous, size-based separation of CTCs from blood (Dean Flow Fractionation (DFF)) which facilitates easy coupling with conventional downstream biological assays. Device performance was optimized using cancer cell lines (> 85% recovery), followed by clinical validation with positive CTCs enumeration in all samples from patients with metastatic lung cancer (n = 20; 5–88 CTCs per mL). The presence of CD133⁺ cells, a phenotypic marker characteristic of stem-like behavior in lung cancer cells was also identified in the isolated subpopulation of CTCs. The spiral biochip identifies and addresses key challenges of the next generation CTCs isolation assay including antibody independent isolation, high sensitivity and throughput (3 mL/hr); and single-step retrieval of viable CTCs.

Using a device implanted in KRAS-driven pancreatic tumors, authors demonstrate that cancer cells incorporate proteins in their microenvironment as a source of amino acids. This work provides a novel approach to study tumor metabolism that could be applied with therapeutic purposes. Mammalian tissues rely on a variety of nutrients to support their physiological functions1. It is known that altered metabolism is involved in the pathogenesis of cancer, but which nutrients support the inappropriate growth of intact malignant tumors is incompletely understood2,3. Amino acids are essential nutrients for many cancer cells4,5 that can be obtained through the scavenging and catabolism of extracellular protein via macropinocytosis6,7. In particular, macropinocytosis can be a nutrient source for pancreatic cancer cells, but it is not fully understood how the tumor environment influences metabolic phenotypes8 and whether macropinocytosis supports the maintenance of amino acid levels within pancreatic tumors. Here we utilize miniaturized plasma exchange to deliver labeled albumin to tissues in live mice, and we demonstrate that breakdown of albumin contributes to the supply of free amino acids in pancreatic tumors. We also deliver albumin directly into tumors using an implantable microdevice, which was adapted and modified from ref. 9. Following implantation, we directly observe protein catabolism and macropinocytosis in situ by pancreatic cancer cells, but not by adjacent, non-cancerous pancreatic tissue. In addition, we find that intratumoral inhibition of macropinocytosis decreases amino acid levels. Taken together, these data suggest that pancreatic cancer cells consume extracellular protein, including albumin, and that this consumption serves as an important source of amino acids for pancreatic cancer cells in vivo.

Blood is a highly complex bio-fluid with cellular components making up >40% of the total volume, thus making its analysis challenging and time-consuming. In this work, we introduce a high-throughput size-based separation method for processing diluted blood using inertial microfluidics. The technique takes advantage of the preferential cell focusing in high aspect-ratio microchannels coupled with pinched flow dynamics for isolating low abundance cells from blood. As an application of the developed technique, we demonstrate the isolation of cancer cells (circulating tumor cells (CTCs)) spiked in blood by exploiting the difference in size between CTCs and hematologic cells. The microchannel dimensions and processing parameters were optimized to enable high throughput and high resolution separation, comparable to existing CTC isolation technologies. Results from experiments conducted with MCF-7 cells spiked into whole blood indicate >80% cell recovery with an impressive 3.25 × 10⁵ fold enrichment over red blood cells (RBCs) and 1.2 × 10⁴ fold enrichment over peripheral blood leukocytes (PBL). In spite of a 20× sample dilution, the fast operating flow rate allows the processing of ∼10⁸cells min⁻¹ through a single microfluidic device. The device design can be easily customized for isolating other rare cells from blood including peripheral blood leukocytes and fetal nucleated red blood cells by simply varying the ‘pinching’ width. The advantage of simple label-free separation, combined with the ability to retrieve viable cells post enrichment and minimal sample pre-processing presents numerous applications for use in clinical diagnosis and conducting fundamental studies.

In blood vessels with luminal diameter less than 300μm, red blood cells (RBCs) which are smaller in size and more deformable than leukocytes, migrate to the axial centre of the vessel due to flow velocity gradient within the vessels. This phenomenon displaces the leukocytes to the vessel wall and is aptly termed as margination. Here, we demonstrate using microfluidics that stiffer malaria-infected RBCs (iRBCs) behave similar to leukocytes and undergo margination towards the sidewalls. This provides better understanding of the hemodynamic effects of iRBCs in microcirculation and its contribution to pathophysiological outcome relating to cytoadherence to endothelium. In this work, cell margination is mimicked for the separation of iRBCs from whole blood based on their reduced deformability. The malaria infected sample was tested in a simple long straight channel microfluidic device fabricated in polydimethylsiloxane. In this microchannel, cell margination was directed along the channel width with the iRBCs aligning near each sidewall and then subsequently removed using a 3-outlet system, thus achieving separation. Tests were conducted using ring stage and late trophozoite/schizont stage iRBCs. Device performance was quantified by analyzing the distribution of these iRBCs across the microchannel width at the outlet and also conducting flow cytometry analysis. Results indicate recovery of ∼75% for early stage iRBCs and >90% for late stage iRBCs at the side outlets. The simple and passive system operation makes this technique ideal for on-site iRBCs enrichment in resource-limited settings, and can be applied to other blood cell diseases, e.g. sickle cell anemia and leukemia, characterized by changes in cell stiffness.